Rear Groan From Stop Esp. L/R Turn

[Fordlandia]

I've owned my '98 4.0 4X4 (Auto O/D, 3.73 Trailer Tow Package) since new... well maintained w/48K miles. Problem: after highway use (50 or more miles), experience low groaning noise upon L or R hand turn from stop at bottom of exit ramp. Noise is only rarely apparent in normal "around town" driving. But when "hot" (e.g rear end fluid hot) after highway use starting up from dead stop, notice groaning (not grind... more of a groan) noise from rear end, especially upon sharper L or R hand turns. This noise then diminishes and stops when car is under power in straightline. It may continue from next 5 or 6 such "from dead stop" turns, but as vehicle "cools" down, seems to lessen and disappear. Along with groan, there is a faint "shutter" which sometimes seems to be originating from from rear end. Have done search of prior posts, and found a few related ones... but would appreciate help with this particular symptom. Thanks in advance!

 

[TPLYNCH]

Welcome to the site. Do you have a Limited Slip rear?? If yes, could be that. Are u sure it is coming from the rear? There was a recall on the PS hoses - they were too narrow- making lots of noise etc....

 

[Fordlandia]

Thanks for the reply. Yes, I do have the limited slip 3.73 that came with the trailer towing package (never towed anything, however). The sound is definitely from the rear. Re. the power steering, I did have that problem early on, was fixed under warranty or recall.

I'm wondering if I just need to drain and replace rear differential fluid or add additive. Could it be that the limited slip "not slipping" on turns due to lubricant breaking down when hot? Any ideas would be appreciated.

 

[SWLathrop]

Since you have a L/S rear axle, you already have synthetic gear lube in it. However, the groaning noise your getting when turning is the early warning sign that the lube needs changed. The clutch packs are not slipping properly. Regardless of the fact that it is a synthetic, crud in the rear axle will cause this problem. It gets sucked in via the breather tube on the axle housing. If not changed, it will lead to premature wearout of the clutch packs. Thus, turning your L/S into an open Diff. I've ran AMSOIL for 13 years in my 88 Ranger S/C 4X4 with front and rear factory L/S axles. I would get about 30,000 miles of use before the groaning would reappear. And that was with or with out the Ford L/S additive. Hope this helps.

 

[orval]

Did you ever get a definitive answer on your problem. What you described is EXACTLY what I am experiencing with my 96 XLT.

I had considered the rear diff as well. Upon inspection, I noticed that the rear seal was throwing out a bit of fluid. I topped up the diff but didn't drain it. I still have the same problem....and like you described only when HOT...and turning under load (i.e. from a stop up a slight grade)

I have taken it to a Ford dealer with no luck. They tried to charge me an analysis fee for someone to ride with me and listen. The guy said.. "Yeah, I hear it but I don't know what it is.." That'll be $70

 

[Fordlandia]

Yes, my problem was solved when I took the advice of SWLathrop (see post above yours). When I drained and replaced the rear differential lube (inc. adding the small bottle of the special "limited slip" additive Ford dealers sell for the 3.73 LS rear), the noise stopped completely. Hope it works for you!